Recent Advances of Freestanding Cathodes for Li-S Batteries

Lithium-sulfur batteries (LSBs) with high energy density and low cost have been recognized as one of the most promising next-generation energy storage systems. Although it has taken decades of development, the practical application of LSBs has been hindered by several inherent obstacles, particularly the severe shuttle effect and sluggish reaction kinetics in the sulfur cathode. Various strategies have been proposed to address these problems via rational design of electrode materials and configurations. Freestanding sulfur cathode could be a promising strategy to improve the sulfur mass loading at the cathode level and energy density of LSBs. This minireview will briefly summary the recent advances in freestanding cathodes for LSBs. The advantages and disadvantages of various freestanding cathodes are discussed and the prospects for the development of flexible cathodes are envisioned.     

Nb(iPrNPMe2)3Fe–PMe3: A potential high reactivity heterobimetallic catalyst for acetylene cycloadditions

Alkynes cycloaddition reactions are powerful tools for constructing cyclic molecules with optimal atom efficiency, but these reactions cannot proceed at ambient temperature without transition-metal catalysts. In this work, a heterobimetallic complex featuring an Nb–Fe triple bond, Nb(ⁱPrNPMe₂)₃Fe–PMe₃, has been evaluated as the potential catalyst for acetylene cycloaddition, using density functional theory. The calculated results show that the singlet-state (i.e. ground-state) Nb(ⁱPrNPMe₂)₃Fe–PMe₃ can be applied to benzene synthesis, but is not suitable for cyclobutadiene. Benzene can be obtained easily at room temperature and is the unique product on the singlet potential surface. The irradiation of infrared-red light can drive the excitation of singlet Nb(ⁱPrNPMe₂)₃Fe–PMe₃ to its triplet state. Both benzene and cyclobutadiene can be formed on the triplet reaction potential surface due to their low energy barriers. Therefore, Nb(ⁱPrNPMe₂)₃Fe–PMe₃ is a potential high reactivity heterobimetallic catalyst for the cyclotrimerization of alkynes. In the reaction process, the catalytic active site of Nb(ⁱPrNPMe₂)₃Fe–PMe₃ moves from niobium to iron.     

A new solution of reducing polymer optical fiber losses

Polymethyl methacrylate (PMMA) is one of the most commonly used optical materials. However, the application of it in the area of optical communication is strongly limited by the intrinsic absorption loss of carbon-hydrogen stretching vibration. In this paper, we present a method to solve the problem by adopting the hollow-core fibers with cobweb cladding structure. The fibers use a single dielectric material and may solve the problem of structural support. Thus the feasibility of the “OmniGuide” fibers is improved, while a series of advantages of the “OmniGuide” hollow-core fiber are retained. It is promising that a fiber with low transmission loss, high bandwidth, large-core, and low costs can be designed and fabricated using PMMA. At the same time, a very broad range of the wavelengths (from visible to near infrared region, for instance, wavelengths at 0.65-1.12 μm, and even 1.30 μm, 1.54 μm and their neighbors) may be adopted for signal wavelength.     

Energy loss effect in high energy nuclear Drell-Yan process

The energy loss effect in nuclear matter, which is a nuclear effect apart from the nuclear effect on the parton distribution as in deep-inelastic scattering process, can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of the nuclear parton distribution studied only with lepton deep-inelastic scattering experimental data, the measured Drell-Yan production cross sections for 800 GeV proton incident on a variety of nuclear targets are analyzed within the Glauber framework which takes into account the energy loss of the beam proton. It is shown that the theoretical results with considering the energy loss effect are in good agreement with the FNAL E866 data.Arrival of the final proofs: 24 June 2003     

利用半导体光放大器进行光脉冲消基座的理论研究

提出了一种利用半导体光放大器(SOA)联合可调谐光滤波器进行高阶孤子压缩消基座的新方法.进行了详尽的理论分析和优化.数值计算表明,在一定条件下,这种方法能够在不展宽脉冲的前提下,对基座进行有效地抑制.     

The Exact Hausdorff Measure Function of the Level Sets of Multi-parameter Symmetric Stable Process

In this paper, we investigate the Hausdorff measure for level sets of N-parameter Rd-valued stable processes, and develop a means of seeking the exact Hausdorff measure function for level sets of N-parameter Rd-valued stable processes. We show that the exact Hausdorff measure function of level sets of N-parameter Rd-valued symmetric stable processes of index α is Ф（r） = r^N-d/α （log log l/r）d/α when Nα 〉 d. In addition, we obtain a sharp lower bound for the Hausdorff measure of level sets of general （N, d, α） strictly stable processes.     

Fermi能区核－核碰撞的平衡前中子发射

利用ＢＵＵ模型模拟核－核碰撞３６Ａｒ＋１０８Ａｇ（３５Ｍｅｖ／ｕ）、１４Ｎ＋１０８Ａｇ（３５ＭｅＶ／ｕ）中的平衡前中子发射．模拟结果与唯象的运动源拟合给出的中等速度源成份相吻合．这说明中等速度源成份产生于核－核碰撞的早期，对应平衡前发射．并从级联碰撞的角度定量地研究了平衡前发射的持续时间     

Poly[[diaqua(N,N‐dimethylformamide‐κO)manganese(II)]‐μ3‐sulfato]

In the title complex, [Mn(SO₄)(C₃H₇NO)(H₂O)₂]_n, each Mn^II ion has a distorted octahedral geometry formed by three O atoms of three different sulfate groups, one O atom of a dimethylformamide ligand and two water molecules. The sulfate groups act as tridentate bridging ligands connecting the Mn^II ions into a two‐dimensional layer structure which can be regraded as a 4.8² network.     

大豆中二硝基苯胺类除草剂多残留的气相色谱法定量检测及质谱确证

建立以凝胶渗透色谱法(GPC)和固相萃取法(SPE)及气相色谱法(GC)联用技术测定大豆中10种二硝基苯胺类除草剂(氟乐灵、乙氟灵、环丙氟、氯乙氟灵、仲丁灵、异乐灵、二甲戊乐灵、二硝胺、氨基丙氟灵和磺乐灵)多残留检测方法.目标农药经正己烷饱和的乙腈提取,凝胶渗透色谱除去大豆中大部分油脂及色素,再经Florisil柱净化和富集,依次用6 mL二氯甲烷和6 mL二氯甲烷+丙酮(99+1)洗脱.目标农药采用电子捕获检测(GC/ECD),外标法定量,并经质谱(MS)确证.两个添加水平重复6次,回收率分别为74%～105%和59%～105%;相对标准偏差＜20%;检出限为1.8～7.6 μg/kg;定量限为6～38 μg/kg.